Phosphate buffered saline

Phosphate buffered saline (abbreviated PBS) is a buffer solution commonly used in biological research. It is a water-based salt solution containing sodium chloride, sodium phosphate, and, in some formulations, potassium chloride and potassium phosphate. The buffer's phosphate groups help to maintain a constant pH. The osmolarity and ion concentrations of the solution usually match those of the human body (isotonic).

Applications

PBS has many uses because it is isotonic and non-toxic to cells. It can be used to dilute substances. It is used to rinse containers containing cells. For example, PBS with EDTA is also used to disengage attached and clumped cells. Divalent metals such as zinc, however, cannot be added as this will result in precipitation. For these types of applications, Good's buffers are recommended.

Preparation

There are many different ways to prepare PBS. Some formulations do not contain potassium, while others contain calcium or magnesium^[1]. Generally, PBS contains the following constituents:

One of the common composition of PBS

Salt	Concentration	Concentration
(—)	(mmol/L)	(g/L)
NaCl	137	8.01
KCl	2.7	0.20
Na2HPO4 • 2 H2O	10	1.78
KH2PO4	2.0	0.27
pH	7.4	7.4

The simplest way to prepare a PBS solution is to use PBS buffer tablets. They are formulated to give a ready to use PBS solution upon dissolution in a specified quantity of distilled water. They are available in the standard volumes: 100, 200, 500 and 1000 mL ^[2].

If used in cell culturing, the solution can be dispensed into aliquots and sterilized by autoclaving (20 min, 121°C, liquid cycle). Sterilization may not be necessary depending on its use. PBS can be stored at room temperature, but may warrant refrigeration to prevent bacterial growth if solution is not sterile and is kept for long periods of time. However, concentrated stock solutions may precipitate when cooled and should be kept at room temperature until precipitate has completely dissolved before use.

References

1. ^ Dulbecco, R. et al. (1954): Plaque formation and isolation of pure lines with poliomyelitis viruses. In: J. Exp. Med. vol. 99 (2), pp. 167-182. doi:10.1084/jem.99.2.167 PMID 13130792
2. ^ Medicago AB, (2010) Phosphate bufered saline specification sheet